The present invention relates generally to environmental sampling, and more specifically to the calibration of sampling equipment.
Sampling and monitoring the waste stream of industrial apparatus is often required by governmental regulations. Whether the waste stream be liquid, gas, or gas with particulate matter, there are many systems employed to carry out such sampling, which can assist the owner/user of the apparatus being monitored to maintain proper (i.e., legal) levels of specific components of the stream, thereby avoiding violations and accompanying sanctions. Given their role in the industrial process, it is important that the monitoring equipment provide accurate readings for the components it measures.
One system for monitoring gas streams with particulate matter is known as a particulate matter continuous emission monitoring system (PM CEMS). A typical PM CEMS includes an optical or other device that produces a signal that is roughly proportional to the mass concentration of particulate matter in the gas stream. Depending on the regulatory application, the PM CEMS may also use a separate flow monitor to allow calculation of particulate emissions in units of mass per unit time (e.g. pounds per hour). In most cases the relationship between PM CEMS output readings and actual mass emissions is site-specific and must be determined experimentally.
Like any sampling system, it is important for a PM CEMS to be accurate in its monitoring of flue gases. As such, an apparatus for calibrating a PM CEMS would be desirable. It would be particularly desirable to have a calibration method that can be carried out without interruption of operation of the industrial apparatus.
The present invention can address these needs by providing an apparatus and method for calibrating a particulate matter continuous emission monitoring system. The apparatus comprises: a feed unit that supplies particulate matter of a known concentration; an eductor unit connected with the feed unit that receives particulate matter therefrom; a fluidizing unit connected to the eductor that supplies gas to the eductor unit, wherein the particulate matter and gas are combined into a fluidized mixture; and a probe connected to the eductor configured to extend within an industrial stack and deliver the fluidized mixture therein. Such an apparatus can provide accurate data regarding particulate matter concentration that can be compared with readings on the PM CEMS and enable a calibration curve to be generated.
In one embodiment, the apparatus includes a tracer gas injection unit connected with the probe. The tracer gas injection unit is configured to inject an easily detectable and non-reactive tracer gas into the probe to combine with said fluidized mixture. The concentration of tracer gas in the stack, which can be detected with a tracer gas analyzer, can be used to calculate the concentration of particulate matter in the stack, which in turn can be compared to the PM CEMS reading.
The present invention also encompasses a method of calibrating a particulate matter continuous emission monitoring system. The method comprises the steps of:
(a) providing particulate matter of a known composition and mass flow rate;
(b) fluidizing and heating the particulate matter with a gas;
(c) injecting the fluidized particulate matter into an industrial stack;
(d) recording the PM CEMS instrument response in units of concentration and/or mass flow rate;
(e) separately determining the emissions of particulate matter in the stack from the known injection rate;
(f) repeating steps (a)-(e) for differing concentrations of particulate matter; and
(g) comparing the PM CEMS instrument response with the calculated particulate emissions to generate a calibration curve for the PM CEMS.
This method may also include the injection of tracer gas into the fluidized mixture, wherein step (e) above comprises the measuring the concentration of tracer gas in the stack as an indicator of particulate matter concentration.
Objects of the present invention will be appreciated by those of ordinary skill in the art from a reading of the figures and the detailed description of the preferred embodiments which follow, such description being merely illustrative of the present invention.